Many types of industrial equipment, such as machine tools, production presses, and other similar heavy equipment pieces, transmit objectionable levels of dynamic shock and vibration forces to the floor areas where they are located during the time they are operating. Also, many types of industrial equipment such as inspection equipment, tool room equipment, machine tools, and others are adversely affected by shock and vibration which may be transmitted to them through the factory floors or foundations on which they are mounted. Additionally, most mechanically operable industrial equipment is susceptible to misalignment, such as, by twisting, sagging or bending, by reason of an uneven floor on which the machine feet are supported, by distortions in the floor due to load or dynamic forces exerted upon the floor by other equipment, and by subsequent settling of the floor. When a machine is not properly aligned, tools, dies and machine components such as bearings or guides are likely to develop excessive friction, waste energy, and wear out faster.
For many years, factory installation and maintenance personnel have attempted to alleviate these problems by using resilient mounts to cushion vibration or shock and by painstakingly shimming up the equipment at various support points to improve alignment. Such equipment is sometimes bolted to the factory floor or to a massive foundation in an attempt to hold it securely in place. The inadequacy of these procedures for optimizing equipment performance has become increasingly apparent to those who have made a serious study of the operational dynamics of industrial equipment. Moreover, as production equipment continues to become more sophisticated and costly, it is increasingly apparent that a more scientific approach is needed, not only to the initial installation of such equipment, but also to continuously monitoring its performance thereafter over a long period of time.
Machine beds are designed to be level and flat to very close tolerances in order for the tools therein to produce parts to close tolerances required and to keep the dies from wearing out prematurely. When the feet of a machine are set down directly floor which is not level or flat, the machine bed is prevented from being level or flat as originally constructed. This interferes with the ability of the machine to do precise work and causes undue wear and tear on the machine, and its operating parts.
Adjustable mountings, such as those covered by U.S. Pat. Nos. 3,332,647 and 4,047,427, are designed to support machines on an uneven floor in such a manner that the bed of the machine is both level and flat to extremely close tolerances. Each mounting is comprised of a support housing for supporting one of the machine's feet; a resilient cushion for cushioning impact forces, for isolating vibration, and for reducing noise; a bearing member for distributing weight and dynamic forces uniformly over the area of the resilient cushion; and a member, called an adjustment member, for adjusting the space between the bearing member and the support member. Hereinafter, familiarity with these mountings will be assumed.
In installations where the machine bed is not level, the adjustment members in the mountings supporting the low side of the machine are adjusted to increase the spacing between the bearing members and support members in those mountings, thus raising that side of the machine until the bed is level in that direction. A machinist's level is usually used for detecting which way the machine bed is sloping and for determining how low that end of the machine is, as well as for determining when to stop adjusting the adjustment members. This procedure is repeated in a direction 90 degrees from the first.
However, levelness in the ordinary sense of the word is not enough to assure proper performance of the machine.
Machines can be leveled to close tolerances and yet be distorted to the point that the wear and tear on the machine and its tools and dies is excessive. For example, it is very important that the bed of a press be flat, as well as level over its entire surface. Most builders of precision machines specify that the level of the bed along each of its four edges be within 0.0005"/ft. in order to achieve the high degree of flatness needed for the machine to work properly. This is usually determined by placing a precision machinists's level on the bed parallel to and close to the four edges of the bed and adjusting the support under each of the four mounting feet until the "bubble" in the vial of the precision machinist's level is within one line of center.
Before the development of precision adjustable machine mountings such as those covered by U.S. Pat. Nos. 3,332,647 and 4,047,427, the only way to attempt to level presses was by setting the machine down, checking the level of the bed at four locations, raising one or more feet off the floor with a jack or pry bar, inserting shims under the feet, lowering the machine, checking the level again at all four locations, and repeating this procedure usually many times. Very seldom, however, were machines leveled to these tolerances, even after many hours and even weeks of time spent on levelling so that they could remain supported to the builder's specified tolerances. The few machines that were originally leveled to close tolerances soon became out of tolerance when shims shifted as a result of the dynamic forces involved in the operation of the machine, or when the floor became distorted when other equipment was moved, or when the floor settled. It took only a few thousandths of an inch of floor distortion or settling to cause a hard mounted machine (one mounted hard to the floor) to lose the levelness and flatness specified by the machine builder.
With the development of the adjustable mountings described in U.S. Pat. No. 3,332,647, it becomes possible to level machines to the close tolerances specified by machine builders over the entire bed of the machine and to do so more quickly and more permanently. These mountings served the additional purposes of controlling vibration and noise and reducing the transmitted impact or shock forces. Simply by adjusting the adjustment member in one or more of the mountings, i.e., the movable member regulating the distance between the member on which the machine foot rested and a second bearing member supported on a well designed cushion member on the machine room floor, it was possible to level the machine to the close tolerances specified by the machinery builders at all four locations on the bed where the precision machinist's level was intended to be placed. In fact, it was found that with these mountings, it was possible to adjust the mountings to achieve even more precise leveling than the 0.0005"/foot tolerances specified by the machine builders, and to do so quickly.
It has been found that this added precision is highly conducive to optimum machine performance and reduced wear and tear on a wide variety of equipment such as a press, and on tools and dies used therein, and the like. This precision is made possible by the combination of two important features of the mountings. These features are (1) a highly precise adjustment member, and (2) the characteristics of the cushion members.
When a machine with four (or more) mounting feet is set down "hard" on a floor, that is in direct contact with a floor and without a cushioning member to absorb vibrations transmitted out of and/or into the machine, differences in floor elevation under the four feet will cause the machine bed to be out of flat, i.e., to have some portions out of a planar surface. For example, if the elevation of the floor under one foot is higher than it is under the other three feet, most of the weight of the machine will be supported by the floor under two mounting feet, namely, the foot at which the floor is high and its diagonally opposite partner, while relatively little of the machine weight will be supported by the floor under the other two mounting feet. Thus, the machine will sag down at the two diagonally opposite corners which are inadequately supported, relative to the two diagonally opposite corners which are excessively supported.
Some machines have been equipped with level adjustment screws which are threaded into tapped holes in the machine feet. The bottom ends of the screws rest directly on the floor. Turning the screws raises or lowers the machine feet when one attempts to level the machine. Such hard mounted leveling devices are capable of rough leveling. However, without the cooperative effects of the resilient member, it is virtually impossible to turn the screw a small enough amount to control height to within the few thousandths of an inch necessary for precision leveling even if the level adjustment screw has a very fine thread. For example, in order to raise or lower a corner of a machine by 0.001", it is necessary to turn a hard mounted leveling screw with 12 threads per inch precisely one eighty-third (1/83) of a turn.
Even if it were possible to make such a small adjustment, it is difficult to maintain a machine in a precisely level condition when such things occur as a lift truck coming by, or another machine being installed nearby, causing vibration of the floor, or repeated or permanent deformation of the floor as a result of these changes. Any such deformation in the floor almost always causes a resultant deformation of a machine which is hard mounted on the floor.
Likewise any permanent settlement of a foundation or floor under one of the machine mounting points reduces the support given to that corner of the machine, as well as the support given to the opposite corner, while it increases the support given to the other two corners. It does not take many thousandths of an inch of floor settlement to have a profound effect on machine flatness and alignment.
It is also very difficult to maintain alignment of machinery that is hard mounted on leveling screws due to dynamic forces caused by the operation of the machine itself and also by dynamic motions of the floor caused by other equipment or vehicles operating nearby. Such dynamic forces cause two types of problems; one, they cause dynamic deformations in the machine during the time the dynamic forces are occurring; and two, they tend to cause the leveling screws to turn, thus losing their adjustment, which causes deformations to continue to exist even after the dynamic forces stop occurring.
When a machine supported on four of the mountings described in U.S. Pat. No. 3,332,647 is set down on the same floor, the distribution of support force will be initially more uniform due to the resiliency of the resilient member in each of the mountings. Therefore, the machine bed will be flatter from the outset, although not necessarily perfectly flat. What deviation does exist can be easily and promptly alleviated by adjusting the adjustment member in at least one of the mountings to distribute the support force even more uniformly.
The resilient member in the mounting supporting the leg at the location where the floor elevation is high and the resilient member in the mounting supporting the diagonally opposite leg will deflect more than the resilient members in the two other mountings due to the difference in spacing between the floor surface and the bottom of the machine feet. The difference in the reaction force with which the various mountings support their respective mounting points is a function of the stiffness of each resilient member and the difference in deflection of the various resilient members. Therefore, for a given difference in elevation, the lower the stiffness, the more uniform will be the force with which the four mountings will support the four corners of the machine. Consequently, the lower the mounting stiffness, the closer the bed will be to a planar surface even before the adjustment member in any of the mountings is adjusted.
It should be especially noted that adjustment of the adjustment member in one of the mounts to bring the machine bed into an almost precisely flat plane is made more accurate due principally to the resiliency of the resilient member in combination with the precision adjustment member, which is preferably a screw threaded element. In this combination, several phenomena occur simultaneously. When the adjustment member in one of the four mountings is adjusted to increase the space between the bearing member (normally adjacent the resilient member) and the support member (normally adjacent the foot of the machine):
(1) the support housing of that mounting and the machine leg supported on that mounting are raised;
(2) the bearing member is pressed down with a greater compression, thus increasing the deflection in the resilient member in that mounting;
(3) the compression in the mounting supporting the opposite corner of the machine is increased; and
(4) the compression in the mountings supporting the other two corners of the machine is decreased.
Thus, by adjusting the adjustment member in one of the under-supported mountings, it is possible to correct an out-of-flatness condition. By adjusting the adjustment members in three of the mountings, it is possible to also support the bed of the machine in a level and flat condition to extremely close tolerances.
It is also possible to maintain the machine bed level and flat due to the effectiveness of the resilient member in keeping distortions in the floor, such as are caused by changes in floor loading, from distorting the machine and in preventing dynamic forces acting on the floor by other machines from affecting machine alignment, either during the dynamic disturbance or subsequent thereto.
Pertinent also to an understanding of the present invention is the fact that further research on the mountings shown and described in U.S. Pat. No. 3,332,647 referred to above revealed that in some cases machine performance could be increased even further by using improved mountings which are described in U.S. Pat. No. 4,047,427. Those mountings each incorporate a load sensor which transmits a signal corresponding to the force with which each mounting supports its respective machine foot. By adjusting the adjustment member in a mounting of this type while observing the force indicators associated with the four mountings, it is possible to achieve a uniform distribution of the forces with which the two pairs of diagonally opposite mountings support their respective machine feet. Thus, adjustment of the adjustment members in the several mounts will support the machine so its bed is in a horizontal plane to even closer tolerances, in some cases even more precisely than those specified by the machine builder. With a little care, it is easy to level machines more accurately than a machinist's level is capable of measuring. In this condition, the machine is capable of producing the most precise parts possible, thereby maximizing both productivity and product quality, with no wear and tear and no downtime due to foundation-induced misalignment.
The mounting types described in U.S. Pat. Nos. 3,332,647 and 4,047,427, which are equipped with threaded adjustment members are now being used to level and isolate heavier and heavier machinery that is so large and heavy that many times it is impossible to manually adjust the adjustment members.
In the case of light machines, the adjustment member may be easy to adjust manually, simply by using a wrench. For heavier machines, the increased normal force on the threads and on the end of the adjustment member make it harder to adjust. For extremely heavy machines, the normal forces are so great that even with the aid of the most effective lubricants it becomes impossible to apply enough manual force or torque to adjust the adjustment member.
In such cases, it has been found necessary to use auxiliary lifting means, such as an hydraulic jack, to lift one corner or one side of the machine to reduce the load on the adjustment member sufficiently to make it possible to adjust it. With the assistance of the jack, it has become possible to support machines weighing as much as a million pounds and even greater, on four mountings such as those covered by U.S. Pat. Nos. 3,332,647 and 4,047,427, and to adjust the adjustment member in each such that the bed of the machine is level and flat to the very close tolerances mentioned above. With the mountings disclosed in U.S. Pat. No. 4,047,427, it is also possible to adjust them to uniformly distribute the forces with which the mountings support extremely heavy machines.
Most heavy machines such as automotive presses are "pit mounted." The bed of such a machine is so deep that the machine feet extend out from the bed at a higher elevation than the bottom of the bed. The feet are supported either on beams or on piers, sometimes as high as 20 feet above the bottom of the pit, and the personnel operating the machines are located on a floor 25 to 30 feet above the bottom of the pit. Often, there is no place to locate a jack on the beam or pier, in which case, in order to lift a corner of the machine, it is necessary to construct a temporary structure from the bottom of the pit to support the jack.
Whether a machine be floor mounted or pit mounted, in any case in which a jack or other lifting device is used in the manner described above to make an adjustment of an adjustment member, one corner of the machine must be raised a sufficient amount to remove most of the static deflection in the resilient cushion member. Even to make adjustments of a few thousandths of an inch, the corner of the machine at the mounting to be adjusted may have to be raised ten times as far, or more, in order to permit that fine of an adjustment.
In the case of a machine supported on three mountings, in order to adjust the adjustment member in one of the mountings, that corner or end of the machine must be raised more than the amount needed to level the machine in order to make even the slightest adjustment of the adjustment member.
In the case of a machine supported on four mountings the problem becomes even more complex. When one corner is raised to permit adjustment of the adjustment member, activation of the jack causes the machine to lean in the direction of the diagonally opposite corner, increasing the load on, and the deflection of, the mounting supporting the opposite corner, while decreasing the load on, and the deflection of, the mounts supporting the other two corners.
Thus, even though the just-described adjustable mountings which have been developed heretofore have been great advances in achieving optimum support for heavy machines, and even though the just-described procedures have proven to be less costly and time consuming than earlier methods, further improvements in accordance with the present invention have been made which result in even greater precision, lower cost, and lower time consumption, as will now be described.